Sir Keir Starmer could be denied a majority at the next general election if the Conservative Party gains just six points in the polls form voters who would have otherwise stayed at home, or supported a minority party.
According to data published by research consultancy Stonehaven, Sunak's party would need to increase their vote share from 26 per cent to just 32 per cent in order to prevent Labour from having a majority.
In this situation, Starmer would miss out on a majority if Labour's projected vote share remains at 40 per cent.
Stonehaven's survey relied on data from around 100,000 people over the course of the last 18 months.
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As a result of Jeremy Corbyn's catastrophic loss at the last election, which saw Labour win just 203 seats, Starmer will need to gain an extra 123 seats in order to secure an outright majority.
This would be the party's biggest turnaround since Clement Attlee came to power after World War II.
Speaking about the data, Stonehaven's Senior Insights Advisor Mark McInnes said the Tories need to focus on "smaller shifts" if they want to "deny Labour a majority".
He told Bloomberg: "Small shifts in the national vote share can result in very significant changes in seats won.
"The Conservatives will be focused on smaller shifts among key demographic groups rather than big leaps, if they are to deny Labour a majority."
Last week, a poll for GB News from People Polling put Starmer’s Labour Party ahead of the Tories by 30 points.
People Polling surveyed 1,581 people exclusively for GB News just after the Prime Minister conducted his reshuffle last week.
Only 19 per cent claimed they would vote for the Conservative Party if a general election were held tomorrow.
Almost half of voters, 49 per cent, revealed they would vote for Labour.